1. Field of the invention
The present invention relates to apparatus and method for applying a cleaning process to a holes which formed on a work piece (an objet to be processed), and to cleaning method for dynamic pressure bearings.
2. Related art
Usually, swarf and process particles (metal chips), as well as burr, are found on the inner wall and the edge surface of a hole right after forming the hole on a work piece. When the metal chips and the burr need to be removed, in general, brush 1 as shown in FIG. 9 is employed. Brush 1 is rotated and inserted in hole 3 formed on work piece 2 in the axis direction thereof; then, the brush 1 is carried out the reciprocated movement for a plurality of times therein to clean the inner wall of the hole.
However, this conventional method for cleaning holes does not remove the above metal chips and burr completely. Although the reciprocated operations are repeated, they are still found thereon.
For example, as shown in FIG. 9, in somtime, when the burr left at projecting corner 3a of L-shape hole 3 and the fine metal chips remain in concave corner 3b, the burr or the fine metal chips could not be removed, because the brush 1 could not reach the projecting corner 3a or the concave corner 3b. 
Also, cleaning of a hole or a screw hole with bottom is extremely difficult for the conventional method. Further, by sweeping the brush 1 into the hole 3, abrasive particles are formed, and removal of particles is required.
As described above, the conventional method provides insufficient cleaning action for holes and low processing efficiency. As a result, the costs of finished products tend to increase, and quality of the products is not reliable. For example, each work piece differs in the shape of metal chips and amount of burr. Therefore, the final product quality after cleaning tends to fluctuate; in other words, it is difficult to obtain stable quality.
The issue of remaining metal chips and burr is quite serious for the inner surface of dynamic pressure bearings which especially require cleanness. The incomplete cleaning of holes as described above may cause lower dynamic pressure characteristics and damage or burning of the dynamic pressure bearings; this may lead to a critical defect.
Therefore, the present invention intends to provide an apparatus and a method for cleaning holes in which a simple configuration provides prompt and excellent cleaning of holes. Also, the present invention intends to provide a method for cleaning in which the inner surface of dynamic pressure bearings is excellently cleaned.
According to an aspect of the present invention, there is provided an apparatus for forming holes comprising:
processing means including ultrasonic processing means for providing ultrasonic cleaning action to an inner wall of a hole formed on a work piece and electrolytic processing means for providing electrolytic cleaning action to said hole;
a cleaning tank for storing a cleaning fluid, which is used as a processing fluid for ultrasonic processing and a processing fluid for electrolytic processing, said work piece being immersed in said cleaning fluid;
a horn electrode tool serving as a horn tool for said ultrasonic processing means and an electrode tool for said electrolytic processing means; and
a support means supporting said horn electrode tool movable forward or backward in relation to said hole formed on said work piece in said cleaning tank.